During the drilling into the earth of an oil or gas well, the bore hole may pass through several different strata, each stratum having its own particular characteristics. If the well casing is not cemented into the bore hole, then the contents of the various strata will become mixed and the products of undesirable strata may block the desirable products of other strata.
The cementing of well casing in a bore hole is well known in the art. For relatively shallow or deep wells the cementing of the well casing in the bore hole has been easily accomplished by pumping cement down the well casing and out the bottom of the casing to fill the bore hole from the bottom. It is then a relatively simple procedure to drill out the cement in the casing after the cement has properly hardened.
However, it has become much more difficult to cement the well because of the pressure gradient involved in pumping the cement from the bore . hole bottom to the top.
The disclosed invention provides a new and unique apparatus and process for cementing well casing in a bore hole. The disclosed invention provides an apparatus and process for cementing the well in at least two stages, one stage located above the other. The apparatus of the invention allows cement to be pumped both from the bottom of the bore hole and from a point somewhere intermediate the bottom and the top.